Two years ago Mark was diagnosed with autism spectrum disorder and as a result, does not speak. He is prone to running away from home or darting into the street or pools, although he can't swim.

Echo was donated to the Fontana family by Guiding Eyes for the Blind and has been invaluable for keeping Mark safe. The 5-year old Lab is trained to automatically brace Mark when he tries to run.

Echo is between 50 and 55 pounds and is wearing a red collar with tags. There was a possible sighting yesterday in New Rochelle, N.Y. Officials ask that anyone who finds Echo bring her to a vet or animal shelter where they can read her microchip and get in contact with the Fontanta family.